What Does a Gas Leak Smell Like? Plus, What to Do if You Detect One

Here's what might be happening if you detect a gas smell in your house.

There are more than 77 million natural gas customers (residential, commercial, and industrial) in the U.S. according to the American Gas Association, which accounted for 32.2% of all energy consumption in 2021 (the latest year with full data). The vast majority of times, gas is used without incidence. However, when a gas leak occurs, it can be hazardous.

“Gas leaks, regardless of their source, are dangerous because natural gas is an extremely explosive and flammable substance—even in small quantities,” says Amanda Veazey, a geologist and the vice president of operations for the Well Done Foundation (WDF).  “Due to the danger posed by uncontrolled natural gas, only trained professionals should attempt to diagnose or correct a leak.”

But what causes a gas leak, and how do you know if you have one? Keep reading to find out how to identify a gas leak, as well as the steps you should take if you suspect you have one.

What is a gas leak and what does it smell like?

First, let’s define a gas leak. “A gas leak is when natural gas leaks from a pipeline and then into an area where it shouldn’t be,” says Lance Sinclair, president of One Hour Heating & Air Conditioning and Mister Sparky.

If you’ve ever smelled rotten eggs, you know that they have a sulfur smell. Sinclair says it’s also possible for your plumbing and even your HVAC unit to have the same sulfur smell. “A rotten egg smell is an indication that you have a natural gas leak somewhere, although most of the time, natural gases are odorless.”

However, to help homeowners quickly identify a gas leak, he says most utility providers will add a rotten egg smell to the gases. “Oftentimes, many gas companies will add methyl mercaptan to natural gases and propane, which helps homeowners detect dangerous leaks, so smells should be taken seriously,” Sinclair says.

But you may not be able to rely solely on a rotten egg smell—because this odor can fade. In fact, in 2021, the National Institute for Occupational Safety and Health (NIOSH) issued a fact and safety sheet advising firefighters that the odorant can fade over time. In 2019, one firefighter in Maine was killed and six others were injured responding to a leak at an office building that had been recently renovated. Odor fade was considered one of the factors that contributed to the firefighters not realizing the building posed an explosion hazard.

Also, a 2018 story by WFAA/ABC 8 in Dallas, TX included interviews with two separate homeowners who stated that they did not smell anything before their respective homes exploded.

Odor fade is most common in new large diameter steel pipes and storage tanks, but can also occur in smaller diameter gas lines that are made of polyethylene.

Related: The 9 Best Smoke Detectors of 2023

How can you identify a gas leak?

Here are more signs of a possible gas leak or issue with your gas.

Odd smells coming the oven

When you leave your food in the oven for too long, you’ll be treated to an unpleasant lesson when a burning smell fills the air.  But that’s not the only time when your nose can be offended by noxious odors. “If your gas stove is not working correctly, it will emit a bad odor—which can signify an issue with your gas connection and sometimes point to a very real danger within your home,” Sinclair warns.

And even if it’s not gas, he says it could be indicative of something burnt or an electrical issue that could cause an electrical fire that will be made worse by the presence of gas.

Odd noises coming from your oven

In addition to odd smells, you should be on the lookout for odd sounds, like a buzzing or ticking noise. If you hear these unusual sounds while the oven is on, Sinclair says it indicates that there’s a loose or broken piece somewhere. “You never want anything to be wrong with any component of an appliance that deals with gas because of the high flammability of gas," he explains.

Food doesn’t turn out right

If “cooked” food from your oven is still raw or barely cooked when you remove it, this could also indicate an issue with your gas stove. “While broken components will cause your oven not to heat correctly, it could also mean that your gas is venting elsewhere, which can be a major issue,” Sinclair warns.

Outdoor signs

Signs of gas leaks can also show up outdoors. “Areas of distressed vegetation around piping, or areas that tend to have puddles with gas bubbles, are also an indication of a potential gas leak underground,” Veazey says.

You should also take note if you have a private water well, as it could have natural gas in it. “Homeowners with private water wells should contact their water well driller for advice if they experience odors, discoloration, or bubbling like carbonated beverages,” Veazey advises.

What should you do if you have a gas leak?

If you suspect that you have a gas leak, don’t use any open flames or electrical devices. “This includes not turning on or off lights, using your phone, or any other electrical appliances, since these sources can ignite the gas,” Sinclair says. Instead, wait until you’re a safe distance away before using your smartphone.

He recommends evacuating the area immediately. “Get everyone out of the house, including the pets, and don’t try to locate the source of the leak or turn off gas appliances before evacuating," he says. You should, however, try to leave the doors and windows open. “As you leave, open doors and windows to allow the gas to disperse and prevent a buildup of gas inside,” he adds.

And certainly, do not smoke. “Smoking near a gas leak is extremely dangerous, as it can ignite gas, so avoid smoking until you are at a safe distance from the leak,” Sinclair recommends.

Once you're at a safe distance away from the area, call your gas company's emergency hotline or customer service number to report the leak and request immediate assistance. “They will send a technician to assess and repair the leak—but do not re-enter the building until it has been deemed safe by professionals who have conducted the necessary repairs and safety checks,” Sinclair says.

Why are gas leaks hazardous?

Fires or explosions (leading to injury or death) are the most dangerous consequences of a gas leak. Even a small spark or open flame can lead to a fire or explosion that can be fatal.

Sinclair also says some gases, like carbon monoxide (CO), can cause adverse health effects just by leaking into the air you inhale. “These gases can displace oxygen in the air, leading to asphyxiation if inhaled in large quantities,” he says. “Symptoms may include dizziness, shortness of breath, loss of consciousness, and, in severe cases, death.”

Even inhaling certain gases at low concentrations can cause immediate or long-term health consequences. “For example, exposure to natural gas can cause symptoms like nausea, headache, and respiratory problems,” Sinclair says. “Prolonged exposure to toxic gases, such as hydrogen sulfide, can result in serious health issues, including organ damage and death.”

In addition, gas leaks can release harmful gases into the environment, adding to air pollution and climate change problems. “Methane, a potent greenhouse gas, is often released during natural gas leaks and has a much higher heat-trapping capacity than carbon dioxide (CO2),” Sinclair explains.

Gas leaks can also damage property. “They can corrode pipes, appliances, and infrastructure over time, leading to costly repairs or replacements.”

So, to prevent gas leaks and hazardous conditions, make sure to stay on top of home maintenance, check your appliances, and keep in mind all the warning signs of gas leaks.

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